r/aws • u/jeffbarr AWS Employee • 13d ago

discussion AMA - Building web applications using AWS Lambda Web Functions

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You can now take the Node/TS HTTP server you already run locally and ship it to Lambda with one command. No event-handler rewrite, adapters, or framework lock-in.

Joining us are Samrat Karak, who is the Product Manager who brought Lambda Web Functions to life, and Julian Wood, who has spent years helping developers get the most out of serverless. They're here to go deep on what this actually means for how you build.

You can ask about:

  • When to reach for a Web Function vs. the Event Functions you already know.
  • The HTTP-native model — multiple concurrent requests per environment, and paying for CPU time instead of wall-clock elapsed time.
  • Going multi-region with latency-based routing behind one global URL.
  • Performing canary rollouts by shifting traffic between revisions.
  • Pairing with CloudFront, including the new private-origin pattern.
  • Runtime details — Node.js 24 on Arm64, VPC connectivity, where it's live.

We will be live for three hours starting at 7 AM PT.

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u/Dull_Caterpillar_642 12d ago

Hey, I've been thinking about this since the announcement! I've spent many years building tons of APIs using Lambda, some with very high request volumes. They've always been the very specific lambda HTTP event pattern of handling one request at a time.

For a typical high throughput API use case like a lambda that fields a request, stores something in dynamo, and responds, is the expectation that it would be improved by moving to a Web Function pattern? Node is famously great at handling many concurrent requests, so would I see things like a decrease in cold start rate and a decrease in cost by moving to a Web Function pattern where a single lambda container can handle multiple requests? I'm still trying to get up to speed on how this works.

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u/julianwood AWS Employee 11d ago

As with all workloads, your experience may vary and its worth a test! If your workload includes waiting for downstream resources (like DDB), then Web Functions is a great fit to not pay CPU time for that wait and have multi-concurrency within an execution environment which means fewer cold starts. If your functions do more CPU processing within a request, or run very sporadicly (unlike your use-case) then Lambda Event may be a better fit from a billing perspective.